Oral and enteral administration require that the medication not be destroyed by the environment of the stomach and digestive enzymes. It is too slow if rapid absorption is required, and cannot be used if the patient is vomiting. Rectal administration in the form of liquids or suppositories circumvents this problem in enteral administration.
Mucosal routes of administration other than the above include absorption through the nasal mucosa, the buccal mucosa, sublingually, or the bronchioles, the latter usually achieved through inhalation of an aerosol. Vaginal and rectal administration are also mucosal routes of medication.
Percutaneous administration is used for iontophoresis or by direct absorption through the skin.
Parenteral administration is used when a drug cannot be given by mouth. The speed of absorption varies greatly with the specific route used, which may be subcutaneous, intravenous, intramuscular, intra-arterial, intraperitoneal, intrathecal, intracardiac, or intrasternal.